<html>
  <head>
	<title> test.html </title>
  </head>
  <body>
	<script type="text/javascript">
	  
	  function getBrowserInfo(){
		  
          var Sys = {};
          var ua = navigator.userAgent.toLowerCase();
          var s;
          (s = ua.match(/msie ([\d.]+)/)) ? Sys.ie = s[1] :
			  (s = ua.match(/firefox\/([\d.]{3})/)) ? Sys.firefox = s[1] :
			  (s = ua.match(/chrome\/([\d.]{3})/)) ? Sys.chrome = s[1] :
			  (s = ua.match(/opera.([\d.]+)/)) ? Sys.opera = s[1] :
			  (s = ua.match(/version\/([\d.]+).*safari/)) ? Sys.safari = s[1] : 0;
		  return Sys 
	  }
Sys = getBrowserInfo();
//以下进行测试
if (Sys.ie) document.write('IE: ' + Sys.ie);
if (Sys.firefox) document.write('Firefox: ' + Sys.firefox);
if (Sys.chrome) document.write('Chrome: ' + Sys.chrome);
if (Sys.opera) document.write('Opera: ' + Sys.opera);
if (Sys.safari) document.write('Safari: ' + Sys.safari);
if(Sys.firefox == '3.0') alert ("firefox 3");
    </script>
  </body>
</html>
